I am not suggesting they overpay but they shouldn't be a $5k-10k difference between them. They seem to use KBB for ICE based trades but not for Tesla trades.I don't think it would make good business sense for Tesla to buy a used Tesla that cost almost the same as what they list as new. That's how crazy Carmax, Carvana, Vroom prices are.
I just traded in my Model Y to a Ford dealer for a Mach-E and they immediately will send that to auction via broker. Telsa does the same.